So, if we were to treat realistic creature design like making a pokémon card, one of the obvious "types" would be volant (flight-capable) creatures, and their biggest downside would be the fact that around 25-20% of their body mass has to be the flight muscles, leaving little room for other things.
This is a problem. Just as legs become dead-weight in flight, flight muscles become dead-weight on land. The best way to counter this is to find as many uses for them as possible.
So, I thought to myself "If it already is around the most vital organs, why not make it more bullet resistant?"
The idea is to enhance the muscle fibers to be more durable without diminishing force-generating capacity, but at the expense of the energy and time it takes for the flier develop them. I mean, dragons already have long lives, might as well make use of it.
But I don't know if that's possible. We most likely want to modify the motor protein itself to have a better shock resistance and tensile strength. Would such modification be possible?